1. Chapter 5 – Sensation Chapter 6 - Perception

2. Sensation Sensation Perception Bottom Up Processing
Top Down Processing

3. Sensation- Basic Principles
Psychophysics
study of the relationship between physical characteristics of stimuli and our psychological experience of them
Light- brightness
Sound- volume
Pressure- weight
Taste- sweetness

4. Sensation- Thresholds
Absolute Threshold
minimum stimulation needed to detect a particular stimulus 50% of the time
Difference Threshold
minimum difference between two stimuli that a subject can detect 50% of the time
just noticeable difference (JND)

6. Sensation- Thresholds
Signal Detection Theory
predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)
assumes that there is no single absolute threshold because ________________________________.

7. Sensation- Thresholds25 50 75
100
Low
Absolute
threshold
Medium
Intensity of stimulus
Percentage
of correct
detections
Subliminal
stimuli
When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”.

8. Sensation- Thresholds
Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion
Examples:
Sensory adaptation- diminished sensitivity with constant stimulation

9. Vision Transduction- conversion of one form of energy to another
Wavelength- the distance from the peak of one wave to the peak of the next
Hue- dimension of color determined by wavelength of light
Intensity- amount of energy in a wave determined by amplitude
brightness
loudness

10. Vision- Spectrum of Electromagnetic Energy

11. Vision- Physical Properties of Waves
Short wavelength=high frequency
(bluish colors, high-pitched sounds)
Long wavelength=low frequency
(reddish colors, low-pitched sounds)
Great amplitude
(bright colors, loud sounds)
Small amplitude
(dull colors, soft sounds)

12. Vision

13. Vision Acuity- the sharpness of vision Nearsightedness Farsightedness
nearby objects seen more clearly
lens focuses image of distant objects in front of retina
Farsightedness
faraway objects seen more clearly
lens focuses near objects behind retina

14. Retina’s Reaction to Light- Receptors
Cones
near center of retina (fovea)
6 million
fine detail and color vision
daylight or well-lit conditions
Rods
peripheral retina
120 million
detect black, white and gray
twilight or low light

15. Visual Information Processing
Feature Detectors
Hubel & Weisel
neurons in the visual cortex respond to specific features
shape
angle
movement
Stimulus
Cell’s
responses

16. Visual Information Processing
Parallel Processing
simultaneous processing of several dimensions through multiple pathways
color
motion
form
depth

17. Visual Information Processing
Trichromatic (three color) Theory
Young and Helmholtz
three different retinal color receptors
red
green
blue

18. Opponent Process- Afterimage Effect

19. Visual Information Processing
Opponent-Process Theory- opposing retinal processes enable color vision
“ON” “OFF”
red green
green red
blue yellow
yellow blue
black white
white black

20. Audition Audition Frequency Pitch the sense of hearing
the number of complete wavelengths that pass a point in a given time
Pitch
a tone’s highness or lowness
depends on frequency

23. Audition Place Theory Frequency Theory
the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated
Frequency Theory
the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

24. Audition Conduction Hearing Loss Nerve Hearing Loss
hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea
Nerve Hearing Loss
hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

25. Touch Skin Sensations pressure warmth cold pain
only skin sensation with identifiable receptors
warmth
cold
pain

26. Pain Gate-Control Theory
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain

27. Taste Taste Sensations Sensory Interaction sweet sour salty Bitter
Umami
Sensory Interaction
the principle that one sense may influence another
as when the smell of food influences its taste

29. Perception
Selective Attention focus of conscious awareness on a particular stimulus

30. Perceptual Organization- Gestalt
Visual Capture
tendency for vision to dominate the other senses
Grouping
the perceptual tendency to organize stimuli into coherent groups

31. Perceptual Organization- Gestalt
Gestalt- an organized whole
Wertheimer, Koffka, Kohler
Grouping Principles
proximity- group nearby figures together
similarity- group figures that are similar
continuity- perceive continuous patterns
closure- fill in gaps
connectedness- spots, lines and areas are seen as unit when connected

32. Perceptual Organization- Grouping Principles

33. Perceptual Organization-Depth Perception
ability to see objects in three dimensions
allows us to judge distance
Binocular cues
retinal disparity
images from the two eyes differ
closer the object, the larger the disparity
convergence
neuromuscular cue
two eyes move inward for near objects

34. Perceptual Organization-Depth Perception
Visual Cliff

35. Perceptual Organization-Depth Perception
Monocular Cues
relative size
smaller image is more distant
interposition
closer object blocks distant object
relative clarity
hazy object seen as more distant
texture coarse --> close fine --> distant

36. Perceptual Organization-Depth Perception
Monocular Cues (cont.)
relative height
higher objects seen as more distant
relative motion
closer objects seem to move faster
linear perspective
parallel lines converge with distance
relative brightness
closer objects appear brighter

37. Perceptual Constancy Perceptual Constancy
perceiving objects as unchanging despite changes in retinal image
color
shape
size

38. Sensory Restriction- Blakemore & Cooper, 1970
Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.

39. Perceptual Interpretation
Perceptual Adaptation
(vision) ability to adjust to an artificially displaced visual field
prism glasses
Perceptual Set
a mental predisposition to perceive one thing and not another

40. Perceptual Set- Schemas
What you see in the center is influenced by perceptual set

41. Perception without Sensation?
Extrasensory Perception
controversial claim that perception can occur apart from sensory input
telepathy
clairvoyance
precognition
Parapsychology
the study of paranormal phenomena
ESP
psychokinesis